The influence of C-factor and light activation technique on polymerization contraction forces of resin composite

Objectives: this study evaluated the influence of the cavity configuration factor (c-factor) and light activation technique on polymerization contraction forces of a bis-gma-based composite resin (charisma,heraeus kulzer). material and methods: three different pairs of steel moving bases were connected to a universal testing machine (emic dl 500): groups a and b - 2x2 mm (cf=0.33),groups c and d - 3x2 mm (cf=0.66),groups e and f - 6x2 mm (cf=1.5). after adjustment of the height between the pair of bases so that the resin had a volume of 12 mm3 in all groups,the material was inserted and polymerized by two different methods: pulse delay (100 mw/cm2 for 5 s,40 s interval,600 mw/cm2 for 20 s) and continuous pulse (600 mw/cm2 for 20 s). each configuration was light cured with both techniques. tensions generated during polymerization were recorded by 120 s. the values were expressed in curves (force(n) x time(s)) and averages compared by statistical analysis (anova and tukey's test,p<0.05). results: for the 2x2 and 3x2 bases,with a reduced c-factor,significant differences were found between the light curing methods. for 6x2 base,with high c-factor,the light curing method did not influence the contraction forces of the composite resin. conclusions: pulse delay technique can determine less stress on tooth/restoration interface of adhesive restorations only when a reduced c-factor is present.